The present invention relates to electronic organ circuitry and particularly to electronic organ circuitry for producing pipe-organ-like tones in response to actuation of keyboard keys and organ stop settings without requiring typically complex keyboard wiring or an excessive number of component parts.
An advantageous circuit configuration employed in prior art electronic organs includes a multiplicity of keyer circuits or simply keyers, one of which is illustrated in FIG. 1. Each keyer gates an audio signal from a sine wave oscillator and shapes this signal for providing an organ sound waveform. In a typical organ there will be a keyer for every note or pitch, and for every organ voice wherein keyers of a particular rank (sometimes also called a keyer) have similar circuitry and distort the sine wave input in a particular manner. Thus, a given rank of keyers may be employed in simulating a flute sound while other ranks may supply a reed sound, a diapason sound, etc.
The keying signal or operative keyer input may be derived from one or more of a plurality of keyboard keys, as illustrated in FIG. 1, which are respectively enabled by different stops. By way of example, a keyer at a given pitch and voice may be keyed from different sources such as the swell division or great division of the organ, and/or at several different footages such as eight foot, four foot, etc. The gating voltages supplied in response to operation of different stops may also vary so as to cause the keyer to pass somewhat different waveshapes producing somewhat different sounds, depending on the stop actuated. In addition, when more than one stop is actuated, the oscillator signal passed by the keyer will be proportionately larger, and possibly different in waveshape, giving a more realistic output as would be produced in a pipe organ by more than one rank of pipes.
The stop enabling input to a keyer is applied via a "diode slide" or simply a "slide" which includes, for example, diodes 46 and 54 in FIG. 1. A large number of slides may be connected at the input of a given keyer, particularly in the case of a theater organ wherein unification is very extensive. Since the number of keyers in an organ of any size may be quite large, it will be appreciated the number of slides in such organ can reach astronomical proportions. In addition, of course, each slide must be wired to separate keys and separate stops on the organ resulting in a very cumbersome wiring problem and presenting limits to theoretically possible design flexibility. Certainly, the alteration of the organ stop circuitry on such an organ can be very difficult or nearly impossible.